Miniature crossbar multiswitch



United States Patent Inventors Appl. No. Filed Patented Assignee Priority Charles Vazquez and (Lu [)ufresnoy. Paris. and Serge Maelstaf, Bagneux. and Michel Barbaut, Savigny-sur-Orge. France 720.248

Apr. 10, 1968 Dec. 29, 1970 International Standard Electric Corporation New York, N.Y.

a corporation of Delaware Apr. 21, 1967 France MINIATURE CROSSBAR MULTISWITCH 8 Claims, 17 Drawing Figs.

U.S. C1 200/175,

200/166: 335/109 Int. Cl .1 H0111 67/14 Field of Search 317/1 12,

117(Cursory). 120: 200/175. 178, 166.1, 166CPC,

166lCTS 166H. l66Bl(Cursory); 335/108, 111, 112, 109

[56] References Cited UNlTED STATES PATENTS 1.951503 4/1934 Reynolds 335/112 2.856.492 10/1958 Heyhal .200/166(1CTS) 2,942 069 6/1960 Hotton et a1 200/175 3.120584 2/1964 Grunfelder et al.... 200/166(.1)X 3.182159 5/1965 Claesson et a1. 200/l66(.l) 3,293.502 12/1966 Beierle 335/112X 3316,512 4/1967 Vazquez et a1. 335/112 ,j' 3,360,626 12/1967 Vazquez 200/175X 3.396157 8/1968 Vazquez ZOO/166(B1) Primary ExaminerRobert K. Schaefer Assistant Examiner-Robert A. Vanderhye Attorneys-C. Cornell Remsen, .lr., Rayson P. Morris, Percy P. Lantzy. .1. Warren Whitesel and Delbert P. Warner ABSTRACT: This is a miniature crossbar switch mounted on a printed circuit board. A number of mechanical features make the switch operate more reliably and in a more efficient manner. One of these features involves a wall, floor, or platform positioned above the printed circuit card to distribute the bending forces of the finger springs and thereby reduce metal fatigue.

SHEET 5 BF 6 PATENTED DEB29 lsm xmmm WY Sid 1 MINIATURE CROSSBAR MULTISWITCH The present invention concerns Crossbar multiswitches and, more particularly, a multiswitch, the features of which, places it in the category of miniature equipments.

of the telecommunication field, particularly in automatic telephony, modern-switching systems often use coordinate connection networks including an important number of Crossbar switches generally arranged in equipments called multiswitch frames. In such equipments, the establishment of a crosspoint brings into play a selection bar, a connection bar, a middle'piece or selecting finger, a set of mobile contact springs mechanically integral one with the other by means of an insulating guide and a set of fixed contacts.

Although the movable parts of these elements undergo only very small movements, they must bring into function a certain number of mechanical pieces and, hence, need a certain rigidity which allows them to support and'tran'smit significant forces. There results dimensions and weight not compatible with the bulk reduction requirements which goes together with progress and improvement of techniques and with the very conception of switching systems which tend to a total or partial electronification.

Besides, due to their mass, the active pieces of standard Crossbar switch equipments have an inertia which limits the operating speed. vNow, if this speed is greatly sufiicient for electromechanical-switching systems, it isnot the same in the case of semielectronic-switching systems, for example, in which multiswitches are generally used to constitute the speech network and are connected to electronic control circuits.

It is therefore necessary to reduce the bulk and increase the operating speed of the m ultiswitches in order that their characteristics and performances be compatible with those of the equipments and circuitsassociated with them.- Of course, there have been trials to reduce the dimensions of standard multiswitches, but this reduction only concerned the dimensions of the components and not the very conception of the operating principle so that this reduction could not be optimal.

' Moreover, the standard multiswitch units necessitate numerous adjustments and tests electrical as well as mechanical,

in the course of manufacture, mounting, operating tests or at the putting into service. Besides, the disadjustments cannot be avoided after numerous operations which raises significant maintenance problems. g

All these considerations lead to employ a' skillful and qualified labour and entail a momentous-loss to time which acts upon the total cost price.

The object of the present invention is to design a miniature multiswitch of new conception, not necessitating any displacement of middle pieces or any particular adjustment.

One of the features of the invention concerns a miniature Crossbar multiswitch mainly constituted by:

a basic support composed of a printed circuit plate used also as support for a set of elastic mobile contact elements;

a frame housing the said set of contact elements, two planes of control bars arranged orthogonally the ones in relation to the others, each bar including apertures ensuring the housing of the said mobile contact elements, two groups of coils respectively controlling the said bars, the restoring devices, of each control bar;

a fixed contact element support provided with grooves for receiving the said elements, openings ensuring the housing and the guiding of the free extremity of the said fixed contact elements and slots transversally arranged with respect to the preceding grooves;

a lid whose ribs house in the said slots whilst holding the fixed contact elements;

such an arrangement avoiding any middle pieces and making it possible to establish a direct connection between the said mobile contact elements and one of the said fixed contact elements by the operation of one of the said selection bars and one of the said connection bars.

Another feature of .the invention relates to the fact that the multiswitch components are mounted on, a printed circuit plate on which are soldered the mobile contact elements, the mechanical holding and the electrical connection of the said multiswitch being done by the plugging of the said plate in a connector, such an arrangement enabling the simplification of the fixture means and the easy mounting of the said multiswitch in miniaturized equipments.

Another feature of the invention relates to the fact that the frame includes four external walls delimiting the housing of the mobile contact elements, the walls comprising at their upper part as many studs are there are selection or connection bars, the said studs engaging in appropriate openings of the said bars in order to ensure their guiding.

Another feature of the invention relates to the fact that two of the external walls have a thickness sufficient to house elastic devices composed of springs acting upon return pieces the upper part of which engages openings provided for that purpose in the said bars. 7

Another feature of the invention relates to the fact that the frame comprises a crossing constituted by two middle walls and a rear wall or plate increasing the rigidity of the said frame, the said walls serving as intermediate supports to the bars.

Another feature of the invention relates to the fact that the rear plate includes as many holes as there are mobile contact elements to traverse the said plate, the said holes including a tapered part facilitating the simultaneous positioning of all the said elements in the said plate. I

Another feature of the invention relates to the fact that the rear wall makes it possible to determine the fiexion point of the mobile contact elements at a predetermined distance of their fixing point onto the printed circuit.

Another feature of the invention relates to the fact that openings are provided in the sole of the frame along the walls in front of which are mounted the bar control coils, each opening ensuring the housing of an extremity of one armature of the said coils, the other extremity engaging in an appropriate cutaway of the corresponding control bar.

Another feature of the invention relates to the fact that all the parts provided for receiving the elements concerning the connection are located at a different level as comparedto the homologous elements concerning the selection, this difference of levels corresponding to the distance which ought to separate the planes in which are situated the connection and selection bars, such an arrangement enabling the control pieces of each type of bars to be identical.

Another feature of the invention relates to the fact that the fixed spring support includes a set of grooves ensuring the housing of the fixed springs, a set of transversal slots the base of which is on the level of the upper part of the said fixed springs and a set of openings enabling the passage of the free end of the mobile contact elements and their guiding.

Another feature of the invention relates to the fact that the lid comprises grooves allowing the free end of the mobile contact elements to move freely in the said lid'and ribs provided for being received in the slots of the fixed spring support in such a way that the face of the ribs be in contact with the upper part of the fixed contact elements at each crosspoint between the said ribs and the grooves of the support housing the fixed springs.

Another feature of the invention relates to the fact that the free end of each mobile contact element traverses the fixed spring support through an L-shaped guiding opening, the motion of the said element being thus orthogonal, at the establishment of a connection under the dependence of the connection and selection bars and at the release when the mobile contact element returns to its rest position, such an arrangement avoiding the wear of the driving teeth of the connection bar which would occur if the mobile contact element, at the release, described a trajectory other than that imposed by the said openings.

"Various further features will be disclosed from the following description which is given, by way of nonlimited example, arid with reference to the accompanying drawings which represent:

of the different parts tion and connectioribars;' 1

FIG. 10, a plan view ona large scale ofthefixed contact ele- 'ment support;

FIG. 11, a sectional view, on a large scale taken alongthe longitudinal axis of a groove for housing the fixed contact elements; e 1

FIG. l2, a sectional view on alarge scale of the lid;

FIGS. 13 to 16, schematic views-explaining the functionof the L-shaped openings of the fixed contact spring support;

FIG. 17, a sectional view on a large scale of the frame and the rear wall.

The description will be started by referring to FIG. l in which are represented the various multiswitch components. The support is constituted by a double-sided printed circuit plate] bearing conducting wires on both faces. The wirings such as 2 enable the establishment of. appropriate connections between soldering terminalareas such as 3 and certain pins of the plug-in part 4. They have only been partially drawn in the FIG, in order to avoid overburdeningit. The plate [is used as direct support of the mobile contact elernents -or springssuch as.5 which, for the same above-mentioned reasons, are

not all represented. These springs are deformable elastic elements having the aspect of a close-wound turn helicoid constituted by a metal wire of circular section and of good electrical conductivity. Such a type. of spring has been described in the US. Pat. No. 3,396,257 which corresponds to a French patent which was originally filed in France on May 26, 1964.

"One extremity of these springs is captive of the plate 1 and is such aspolycarbonate, for example. A sectional view, on a large scale, of the frame 6v is shown in FIG. 17 which there will be reference to in the following description. This frame, practically square, includes a floor or rear wall 7 provided with .holes enabling the passage of the mobile springs and walls 8,

9, l0 and 11 profiled in order to house respectively thefl'exible ribbons or control bars, selection bars 12 and connection .bars 13 a detail of which is shown in FIGS. 2 and 3. These external walls present studs14-15 and 16-17 (FIG. 17) which engage the vertical part 18 or 18' of the T openings provided at each extremity of bars 12 and 13 (seealso FIGS. 2 and 3),.

such an arrangement ensuring an efficient guiding of the bars.

The walls 8 and 11 have a greater thickness than the walls 9 and since they are provided-to house the mechanical-holding devices of the control bars. Such devices enable the holding of the established connection without any electrical power consumption and have been the object of the U5. Pat. application No. 673,791 filed on Oct. 9, 1967, and entitled: Miniature Crossbar Switch with Mechanical Latch." There will be recalled that the springs 102 (FIG. 17) are pressure springs respectively located in housings such as 19, each housing being proper to a control bar. Each spring thus exerts on a return piece 20 a force which maintained it against the external edge of its housing 19; The. extremity 103 of each return piece which is the only part visible in FIG. 1 engages the horizontal part 21 of the T opening 18 of the selection bar 12 is a frame 6 which is made of moulded hard plastic material or of the corresponding connection bar 13 (see FIGS. 2 and 1 3), which definitely positions the control bars.

A crossing constituted by the middle walls 22 ands23 ensures a better rigidity to the frame-and serves asintermediate support to the selection and connection. bars. It will be noted that the wall 22 also includes studs 24 which engageslots25 of the; connection bars 13 (se'e -FIGIB) thus, bringing an addi wv'sm' i the'external walls extend on'bothtional guiding.

The crossing as well as edges of the frame by meansofwings 26 which delimit the lo cations reserved to the coils of the bar control electromagnets.

Each type. of coil-selection coils'27 'or'eonnection coils 28- --is such that it constitutes two groups 'ofieight, each mounted on a. common yoke 96,. This yoke is further placed between two-wings 26, its fastening being ensured on' frame 6, for example, by means of screws which are introduced inthe aper- I tures 29 and 30 and 31 and 32 of the printed circuit plate 1. The terminals of the coils such as 33 are sufficiently long in i order to be connected to'the soldering terminal areas which are either found on the upper face of the plate 1 (soldering terminal areas 3) and allow the connection-of the selection I coils 27 or onthe lower face and ensure the 'solde'ringof the terminals 33 of the connectioncoils 28 which traverse the plate 1 through holes 34. Only two armatures 97 (FIG. 17) of the selectioncoils are shown in theFlG. in order not to overburden it. They are identical for the connection coils and are worked in order to present a part which engages openings 35' (FIG. 17). The position of the coils once mounted on the frame is such that the yoke 96 comes to contact them and that V its edge 104 (FIG. 17) constitutes the pivot'ing'axis of the arf.

matures, the upper part of which engages the horizontal, part 36 of the T'? formed by theopening 18' o'r'uig contif ol bars (FIGS..2 and 3).

It will be noted that the heights of the profiles pf walls 8, 10 and 22 which receive the connection bars are inferior to that l of the homologous profiles of walls 9; Hand 23. This is due to the fact that the connection bars and the selection bars are not positioned in the same plane. There results a difference of levels which corresponds to the distance between the two planes in which the bars operate.

This difference .of levels is also found in the parts of the frame supporting the coils between the wings 26 as well as in openings 19 of the mechanical-holding devices of the control bars' owing to the fact that the ,electromagnet armatures 97 and the return pieces 20 must be placed at different heights according to whether they act upon the connection bars or the selection bars.

Apertures such as 37 are provided in the angles formed by the abutment of the walls and are used to fix by selfstapping screws 48the fixed contact spring support 38 and the lid 39.

The fixed contact spring support 38 is constituted by a plate detailed in FIGS. 10 and 11; its length is such that the part of the spring external to the support 38 is sufficiently long in order that'it is. possible to solder its extremity onto a soldering terminal area of the lower face of the plate 1 corresponding to one of the holes 42. The fixed contact spring support 38 also includes two series of slots 43 transversally positionedwith respect to grooves 41. The slots 43 receive the ribs 44 of the lid 39 which ensures the holding of the fixed springs 40 in the bottom of their grooves. The grooves 98 are provided for the passage and the guiding of the free end of each'of the mobile spring 5 (see details in FIGS. 10 and 11). It is to be noted that the support 38 is not exactly square and shows an extension in the part corresponding to grooves 45, 46 and 47. This extension makes it possible to bring the fixed springs 40 perpendicularly to the holes 42 which are in relation with soldering terminal areas of the invisible face of the plate I, the end of springs 40 being then in a position which prevents them from interfering with the terminals 33 of the selection coils 27.

The lid 39 is made of transparent hard plastic material which enables to see, without disassembling, the active parts of the multiswitch. A detailed view of this lid is shown in'FIG. 12. Screws such as 48 traverse the holes 49 of the lid and the holes 50 of the support 38 in order to fix these elements onto the frame 6 by means of holes 37.

In order to better illustrate the miniaturization of such a Crossbar multiswitch, the overall dimensions of this embodiment are approximately 22 cm X 25 cm'and27 cm thick. In the described example, such a multiswitch includes 16 connection bars and 16 selection bars, each connection corresponding to the establishment of two crosspoints which makes a total of 512 possible contact points. It is obvious that this equipment is nonlimitative and that its binary" character has only been chosen for descriptive purposes, a decimal basis equipment or other basis being quite as much possible.

The operation of this multiswitch which has already been described in the US. Pat. application No. 3,360,626, first filed in France on July 2, I964 and entitled: Switching-selecting device and in the Pat. application Ser. No. 675,791 previously cited. FIGS. 4 to 8 only represent parts of the selection bars 50 and 51 and a partial connection bar 52 in order to sim plify the drawing and the description. Besides, only the active part of the angle of the apertures 53 of the selection bars 12 (FIGS. I and 2) and the tooth 54, active parts of the openings of the connection bars 13 (FIGS. 1 and 3) have been kept.

FIG. 4 corresponds to the rest position of the selection and connection system. In-this position, the selection bars 50 and 51 'are urged in the direction of the arrows F1 and F2 by their mechanical holding devices placed in the housings 19 of FIG. I, that is by the restoring springs which act by means of the armatures 20 upon the selection bars 12 through part 21 of their T openings 18 (FIG. 2). The connection bar 52 is at rest urged in the direction of the arrow F3 by a device identical with that of the device urging selection bars '50 and 51; the armature submitted to the restoring spring acts upon the edge 21 of the opening 18 (FIG. 3) and, in this case like in the previous one, the armature 97 of the selection and connection coils 27 and 28 respectively (FIGS. I and 17) are drawn by parts 36 of the respective openings 18 (FIGS. 2 and 3) and applied in this manner against the walls 9 and of the frame 6 (FIGS. I and I7).

, When it is desired to establish a crosspoint, contrary to current practice in coordinate connection networks, the connection bar is moved before that of selection. As shown in FIG. 5, a current impulse applied to the electromagnet of the connection bar 52 causes the attraction of the armature against its core, the bar 52 being drawn in the direction of the arrow F4- against the restoring spring associated with the other end of the bar 52. At the end of its path, all the teeth, such as 55 and 56, of the bar 52 are disengaged from the corresponding mobile contact elements, such as 57 and 58 (bearing the reference 5 in FIG. 1).

In FIG. 6, it is supposed that the selection bar chosen was the bar SI. By an operation similar to that of the connection bar 52, the selection bar 51 is moved in the direction of the arrow F5, driving the mobile contact spring 58 and leading it opposite the tooth 56 of the connection bar 52.

In FIG. 7, the impulse which holds the electromagnetof the connection bar 52 in operating position is suppressed so that, under the action of its restoring spring, the connection bar 52 returns into its rest position (position identical with that of FIG. 4) driving the contact element 58. However, the impulse fed to the electromagnet of the selection bar 51 having not yet ceased, the mobile spring 58 slides along the side of this bar whilst the restoring spring leads back the connection bar 52 to rest. Finally, the mobile spring 58 comes into contact with two points of the V formed by two adjacent turns of the fixed turn, the impulse which held in operating position the electromagnet of the selection bar 51 has ceased and this bar returns into the rest position that it occupied in FIG.'4 from the fact of the force exorted by its restoring spring in the direction of the arrow F2.

After this sequence, the process of establishing a crosspoint is over. The connection remains established between the fixed spring 59 and the mobile spring 58 although each of the electromagnets may no longer be fed; the particularity of this connection is that its holding does not necessitate electrical power consumption since it is ensured mechanically by the sole action of a spring acting upon the connection bar.

To free the crosspoint, it is sufficient to apply an impulse to the electromagnet controlling the connection bar 52, in order that this bar be shifted in the direction of the arrow F4 and take the operating position shown in FIG. 5. From the fact of its own-elasticity and of the preferable inclination given by the mounting, the contact element 58 follows the bar in its displacement and, when it is found disengaged from the fixed contact 59, slides on the tooth 56 and comes to take up again its position in the bottom right angle-relative to the FlG.,of

the window of the selection bar 51.

In FIG. 9, there are shown some noteworthy positions of the selection and connection elements, the bars being this time shown as normally constituted. The rest position corresponds to the two points A and A situated at the crossing 'of the selection bars 60 and the connection bars 62; in this position, the

apertures made in each of these bars are superimposed. At the points B and B situated at the crossing of the bars 61 and 63, the same case as in FIG. 7 is found, the connection bar being returned to rest, the selection bar still operating, with the difference that the mobile springs 65 and 66 come just to enter into contact respectively with the fixed springs 67 and 68. It will be noted that, in this case, the apertures of the bars 60- -6I and 63 are not exactly superimposed and that there exists a slight shift between them. This shift is explained by the fact that at the precise moment when the springs come into contact, the connection bar hasnot yet finished its path. At the end of this path, the distance corresponding to the shift has been traversed, which is indicated by an elastic deformation of the mobile springs and, consequently, by a maximum contact pressure between the fixed and mobile springs of the crosspoint considered. This position which is that of mechanical holding corresponds to the crosspoints C and C established between the bars 60 and 64 in which the mobile springs 69 and 70 are respectively in contact with the fixed springs 71 and 72 and are held in position by the teeth of-the connection bar 64 which oblige them to incurve, thus improving the contact pressure. In this position, the apertures formed in the selection and connection bars are exactly superimposed as is the case with the crosspoints A and A of the rest position.

By examining again FIG. 9, it is to be noted that the holding or rest condition of the connection bars does not in any way change the possibility of clearance of the mobile springs, the possibility of which is imperative for the correct operation of a multiswitch. Indeed, whatever may be the position in which a connection bar is found, it ought always to be possible to move any selection bar whatever and to find a clearance for the mobile springs not taking part in the connection. Thus, the bar 62 is at rest whilst the bar 64 holds the crosspoints C and C but the mobile springs 73, 74, 75 and 76 have found a clearance by the side of the inclined part of the tooth of the connection bar when the selection bar 61 has been operated to allow the establishment of crosspoints B and B.

FIG. 10 represents a magnified plan view of the fixed spring support 38 of the FIG. 1 and in order to facilitate the interrelation of these FIGS. the same references as in FIG. I will be used in FIG. I0. Moreover, the cross section of the FIG. I1 along the axis of the upper groove 41 of FIG. 10, on the same scale, will make it possible to see the levels of the various profiles of the support 38. There will also be referred to the FIG. 12 which is a cross section view of the lid 39 and enables a better understanding of the way its grooves and ribs cooperate with those of support 38.

n the left of the FIG. 10, there can be recognized the front part of FIG. 1 which includes slots 45, 46 and 47. Three grooves 41 have been represented, two with their fixed springs 40, the other free in order to facilitate the representation of the teeth 75 which ensure the holding in position, in the longitudinal direction, of the fixed springs 40 by the engaging between two of the adjacent turns. L-shaped openings 76 (FIG. 10) which go through the support material 38 between the bottom of the grooves 41 and the lower face 77 (FIG. 11) can be noted. These openings 76 ensure the guiding of the free end of the mobile springs (FIG. 1) which extend through them and may be either in nest position-as the springs 78-or in operating position as the springs 79. The slots 43 are identical with the slots 45, 46, 47 and it can be seen in the FIG. 11, that their depth enables them to be on alevel with the upper part of the fixed springs 40.

Referring also to FIG. l2 which is a cross section view of the lid 39, it is noted that the slots 43, 45, 46 and 47 are designed for housing the ribs 44 (FIGS. 1 and 12) of the lid, this arrangement determining the holding in position of the fixed springs 40 at the bottom of the slots 41, the face of the ribs 44 coming into contact with the upper part of the springs 40. The lid 39 also includes recesses 80 in which can move the free ends of the mobile springs 5 FIGJ); indeed, as it can be seen in FIG. 11 with the mobile springs 79, a certain part of the length of these springs extends from the upper face 81 of the support 38 and may freely move in the lid 39.

By examining again FIG. 10, there can be seen a slot 99, almost central, wider than the others. It is arranged above the internal wall 23 of the frame 6 (FIG. 1) and ensures the housing of a rib 100 of appropriate dimensions of the lid 39 (FIG. 12).

It is noteworthy that it is at the level of this groove 99 that the fixed springs 40 are or are not cut in order to realize multiswitches capable of switching two'or four wires. Indeed, in two-wire switching,the selection bars driving pairs of mobile springs (see FIG. 9, for example), one of this pair is placed under the dependence of the connection bar chosen, the two moving springs being thus brought respectively into contact with two fixed springs. In this case-it is the case of FIGS. 1, l0 and l1-an extremity of the fixed springs 40 must be sufficiently long in order to be connected with an appropriate circuit of the printed wiring of the plate 1. The fixed springs 40 are then cut only at'the level of the other edge of the support 38 since they must be accessible to the mobile springs operated by any connection bar.

However, in the case when the circuits to be established necessitate the simultaneous switching of four wires, as each connection bar can only operate two mobile springs and realize only two contacts at the same time, it becomes necessary to control in parallel two connection coils the two bars of which will each drive a pair of mobile contacts thus allowing the establishment of four simultaneous contacts. As these two pairs of mobile contacts have initially been operated by the same selection bar, they are situated on the same level and come into contact with the same two fixed contacts. It is therefore necessary to divide the multiplying formed by each of the fixed springs into two distinct parts each connected to a respective printed circuit on the plate 1. This is done very simply by cutting the fixed springs 40 at the 'level of the slot 99, each part of the fixed spring placed on each side of this slot being accessible to a pair of mobile springs operated by a connection bar belonging to one of the two homologous groups of connection bars.

FIGS." 13 to 16 represent, on a very large scale, simplified views explaining the role of the L-shaped openings 76 of the fixed spring support of the FIG. 10. In FIGS. 13 and 14, it has been assumed that the fixed spring support 38 only included openings 90 of the same shape as those of the selections bars and, to simplify the graphic representation, that these openings exactly superimposed in rest or operating position (connection electromagnet deenergized). In FIG. l3rest position-the mobile spring 82 comes in the bottom right angle of the FIG. from the fact of the inclination given by its mounting on the printed circuit plate. However, with normal dimensions, the distance between the spring 82 and the fixed spring 83 being very small, it may happen that subsequent to a shock, the spring 82 leaves this rest position and comes into contact with the fixed spring 83 as it is indicated by the spring 84 represented by a dotted line. There results an untimely contact giving the erroneous indication of a connection.

In FIG. 14, the mobile spring 82 is in operating position, that is in contact with the fixed spring 83. At the release. the connection bar is operated so that the tooth 85 moves in the direction of the arrow 86. The mobile spring 82 is thus no longer held against the turns of the spring 83 and goes back to its rest position of .FIG. 13 according to an approximative trajectory indicated by the arrow 87. Now, by describing this trajectory, the mobile spring 82 comes to rub against the sharp angle 88 of the tooth 85 which effects its motion 86. As the spring is metallic and the tooth in insulating material of less mechanical resistance, there results a wear of the angle 88 which may become such that the tooth85 is no longer capable of holding the mobile spring 82 between two consecutive turns of the fixed spring 83.

The L-shaped of the openings of the fixed spring support 38 makes it possible to avoid these drawbacks and even offers momentous operating facilities. In FIG. 15, the mobile spring 82 is at rest and it can be seen that its untimely displacement could only be lateral, any possibility of coming into contact with the fixed spring 83 being avoided by means of the edges of the opening 89 and by the connection tooth 85.

FIG. 16 corresponds to the release of a connection established between the mobile spring 82 and the fixed spring 83, the tooth 85 of the connection bar being moved in the direction of the arrow 86. It can be seen that due to the vertical" bar of the L opening 89, the mobile spring 82 cannot describe the trajectory indicated by the arrow 87 of FIG. 14 and performs an orthogonal motion. It must follow the tooth 85 in its displacement and escapes from it to come back to the rest condition in a position where there is no danger of wear for the extremity of the tooth.

This orthogonal guidance presents also another advantage relating to the operating reliability of the multiswitch. Indeed, as the connection and selection electromagnets are controlled by short impulses, it is necessary that there be a certain synchronism between these impulses. Thus, the control impulse of the selection bar must be sufficiently long in order that the connection bar has had enough time to drive the mobile spring and hold it against the fixed spring before it ceases (FIGS. 6 and 7). If this impulse is too short or if there is a shift between the control impulses of the selection-and connection bars, in the case of FIG. 14 for example, the tooth 85 has not the time to bring the spring 82 in the V of the fixed spring 83 before the edge 101 of the opening of the selection bar moves off from the spring 82 to return to the, position shown in the FIG. The mobile spring hence returns to the rest position and the connection cannot be established.

In the case of a L guidance such drawbacks are avoided. If the selection bar returns to rest too rapidly, that is if the edge 101 of its opening returns too quickly to the position it has in FIGS. 15 and 16, or if the connection bar operates too slowly with respect to the time normally expected, it suffices that the mobile spring 82 be slightly engaged in the vertical" bar of the L opening, as represented in FIG. 16, in order that it cannot escape and that it is possible to the connection bar to pursue its connection movement in the direction of the arrow 91, the tooth 85 then pushing the spring 82, whose guiding is ensured by the edges of the L opening, towards the fixed spring 83.

In the description of FIG. 1, it has been seen that the frame 6 includes a rear wall 7 provided with openings for the passage of the mobile springs 5. FIG. 17 is a transverse cross section view of the frame 6 along the axis of a row of these openings, there can be seen the elements of F IG. 1 such as the printed circuit plate 1 with only two mobile springs 5 represented, the frame 6 with the wing 26, the external wall 10 against which come to lean the armatures 97 of the connection coils, the internal wall 22 in cross section, the housings 19 provided in the wall 8 to receive the restoring and mechanical-holding devices of the connection bar, the external wall 11 and its guiding studs 14.

In FIG. 1, there has been seen that the mobile springs 5 were placed on the printed circuit plate 1. They are then soldered, for example, by wave soldering but due to the fact that the holes of the plate 1 are necessarily of diameter slightly larger than that of the mobile springs 5 and to the wetting capacity of the solder, the latter tends to go up the turns of the springs 5 and to extend beyond the level represented by the upper face of the plate 1. Now, if no wall 7 existed, the flexion point of the mobile springs 5 would be badly defined. Owing to the function of the rear wall 7, the flexion point is brought from 92 to 93. As the frame 6 is mounted on the printed circuit plate 1 after the soldering of the mobile springs 5, holes 95 have been provided opening on widely tapered apertures 94 in order to facilitate the mounting of the frame 6 and of its rear wall 7 on all the mobile springs.

It is clear that the preceding description has only been given as an unrestrictive example and that numerous alternatives may be considered without departing from the scope of the invention.

SUMMARY The invention concerns a miniature Crossbar multiswitch made up of a basic support constituted by a printed circuit plate also used as support for a set of mobile contact elements, a frame' housing this set, two planes of selection and connection bars and their control coils as well as the restoring devices of the bars, a fixed contact elements support and a lid.

We claim:

l. A miniature crossbar multiswitch comprising a printed circuit card having a boxlike frame mounted thereon, an orthogonal array of contact operating members extending across said frame, means for individually and selectively operating and releasing said members, said operating means being mounted on said frame adjacent individually associated ones of said members, and ribbed means for covering said frame, said ribbed means including grooves running transverse to said ribs for supporting said fixed contacts, the space between the ribs of said ribbed means forming guideways for partially guiding said movable contacts, said movable contacts being controlled by said orthogonal array of contact-operating members.

2. The multiswitch of claim 1, wherein each said fixed contact is a stretched spring, and said grooves include teeth for stabilizing and supporting the position of said stretched springs in said grooves.

3. A miniature crossbar multiswitch comprising a printed circuit card having a boxlike frame mounted thereon, an orthogonal array of contact-operating members extending across said frame, means for individually and selectively operating and releasing said members, said operating means being mounted on said frame adjacent individually associated ones of said members, a lid on said frame, a plurality of fixed contacts by said lid, a plurality of movable contacts supported by said printed circuit card and projecting outwardly through openings in said lid, said movable contacts being moved into and out of contact with said fixed contacts responsive to said operation and release of said orthogonal array of members, and a floor plate in said frame positioned above and parallel to said printed circuit card, said floor having a plurality of openings therein, a plurality of flexible mobile contact means extending through said openings in said floor to a point of attachment on the printed circuit card whereb each mobile contact may be flexed at said opening in said oor instead of bending at the point of its attachment to said printed circuit card, the edge of each opening in said floor being shaped to distribute the flexing over an extended length of the mobile contact thereby minimizing material fatigue resulting from the bending of the contact.

4. The multiswitch of claim 3 wherein said openings in said floor plate are tapered.

5. The multiswitch of claim 4, including means for locating all switch parts in parallel planes which are positioned at different distances away from and parallel to said printed circuit card, the members in one coordinate direction of said orthogonal array being in one of said planes and the members in the other coordinate direction of said array being in another of said planes, and a plurality of fixed contact springs in yet another of said planes, and a plurality of said movable contacts are elongated, mobile flngerspring contacts in said frame and extending freely from said printed circuit card approximately perpendicular to said planes and through the crosspoints formed by the array of contact coordinate members.

6. The multiswitch of claim 5 wherein said orthogonal array comprises flexible ribbons stretched across the top of said frame and held between two upstanding armatures, said armatures being mounted on said frame and spring biased to assume a normal position.

7. The multiswitch of claim 6 and pulse operated magnetic means for momentarily pulling said armatures against said spring bias.

8. The multiswitch of claim 5 wherein said crosspoints of said orthogonal members have an operating window means for moving said elongated contacts to a closed position, said elongated contacts being set at a mounting angle in said printed circuit card, said angle being oriented relative to said operating member so that said contact moves under its own spring bias to a release position without engaging said operating member. 

